Method of communication using frame

ABSTRACT

A device and method for communicating by a mobile communication terminal in communication with a base station. The method according to an embodiment includes exchanging a frame of data with the base station. The frame of data includes a) a plurality of first subframes each having a first number of orthogonal frequency division multiple access (OFDMA) symbols, and b) a plurality of second subframes each having a second number of orthogonal frequency division multiple access (OFDMA) symbols different from the first number. A first and a last subframe each includes one of the plurality of first subframes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 12/372,563 filed on Feb. 17, 2009, which claims the benefit ofpriority of U.S. Provisional Application Ser. No. 61/029,372 filed onFeb. 17, 2008, U.S. Provisional Application Ser. No. 61/029,573 filed onFeb. 19, 2008, U.S. Provisional Application Ser. No. 61/037,694 filed onMar. 18, 2008, U.S. Provisional Application Ser. No. 61/118,443 filed onNov. 27, 2008, U.S. Provisional Application Ser. No. 61/118,444 filed onNov. 27, 2008, U.S. Provisional Application Ser. No. 61/140,055 filed onDec. 22, 2008, U.S. Provisional Application Ser. No. 61/141,660 filed onDec. 30, 2008, Korean Patent Application No. 2008-0057869 filed on Jun.19, 2008, and Korean Patent Application No. 20080058814 filed on Jun.23, 2008. The entire contents of the each of these applications arehereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to wireless communications, and moreparticularly, to a method of communication using a frame in a wirelesscommunication system.

2. Related Art

The Institute of Electrical and Electronics Engineers (IEEE) 802.16standard, incorporated herein by reference, provides a technique andprotocol for supporting broadband wireless access. The standardizationhad been conducted since 1999 until the IEEE 802.16-2001 (incorporatedherein by reference) was approved in 2001. The IEEE 802.16-2001 is basedon a physical layer of a single carrier (SC) called ‘WirelessMAN-SC’.the IEEE 802.16a standard, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’are further added to the physical layer in addition to the‘WirelessMAN-SC’. After completion of the IEEE 802.16a standard, therevised IEEE 802.16-2004 standard (incorporated herein by reference) wasapproved in 2004. To correct bugs and errors of the IEEE 802.16-2004standard, the IEEE 802.16-2004/Corl (hereinafter, IEEE 802.16e) wascompleted in 2005 in a format of ‘corrigendum’(incorporated herein byreference).

Recently, standardization on the IEEE 802.16m is in progress as a newtechnical standard based on the IEEE 802.16e (incorporated herein byreference). The IEEE 802.16m (incorporated herein by reference), whichis a newly developed technical standard, has to be designed to supportthe previously designed IEEE 802.16e. That is, a technology (i.e., IEEE802.16m) of a newly designed system has to be configured to operate byeffectively incorporating a conventional technology (i.e., IEEE802.16e). This is called backward compatibility. The backwardcompatibility considered in the design of IEEE 802.16m is as follows.

First, a user equipment (UE) employing a new technology has to operatewith the same performance as a base station (BS) (or a UE) employing aconventional technology. Hereinafter, for simplicity, any system (e.g.,UE, BS, etc.) employing the new technology is referred to as a newsystem, and any system (e.g., UE, BS, etc.) employing the conventionaltechnology is referred to as a legacy system. Second, the new system hasto operate in the same radio frequency (RF) subcarrier and the samebandwidth as those of the legacy system. Third, the new BS has tosupport a case where the new UE and the legacy UE coexist in the same RFsubcarrier, and overall system performance has to be improved by a ratioof the new UE. Fourth, the new BS has to support a handover of thelegacy UE and a handover of the new UE such that their handoverperformances conform to those of legacy BSs. Fifth, the new BS has tosupport both the new UE and the legacy UE to the same level as thatsupported by the legacy BS to the legacy UE.

The new BS performs scheduling on radio resources to be allocated to thelegacy UE or the new UE within a bandwidth that can be supported by thenew BS. Scheduling of the radio resources can be performed in a logicalframe consisting of a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a time domain and a plurality ofsubchannels in a frequency domain. Therefore, there is ongoing researchon a frame structure in which the IEEE 802.16m system can supportbackward compatibility with the IEEE 802.16e system.

In particular, in a case where time division duplexing (TDD)-type framestructures having different cyclic prefix (CP) lengths coexist inneighbor cells, a boundary between downlink and uplink regions mayoverlap, which may result in mutual interference. Accordingly, there isa need to design a TDD frame structure capable of preventinginterference between the TDD frame structures coexisting in the adjacentcells.

In addition, although a system profile based on the conventional IEEE802.16 standard supports only a TDD scheme, there is an attempt to alsosupport a frequency division duplexing (FDD) scheme in which uplinktransmission and downlink transmission are performed in differentfrequency bands. Accordingly, for convenience of system design andhardware sharing, there is a need to design an FDD frame structurehaving a common feature with the TDD frame structure.

SUMMARY

The present invention provides a time division duplexing (TDD) framehaving various cyclic prefix (CP) lengths to mitigate interferencebetween uplink and downlink transmissions.

The present invention also provides a method for transmitting afrequency division duplexing (FDD) frame having a common feature withthe TDD frame.

In an aspect of the invention, there is a method of communicating by amobile communication terminal in communication with a base station. Themethod includes exchanging a frame of data with the base station. Theframe of data includes a plurality of first subframes each having afirst number of orthogonal frequency division multiple access (OFDMA)symbols, and a plurality of second subframes each having a second numberof orthogonal frequency division multiple access (OFDMA) symbolsdifferent from the first number. A first and a last subframe eachincludes one of the plurality of first subframes.

The step of exchanging a frame of data with the base station may includeat least one of transmitting the frame of data to the base station andreceiving the frame of data from the base station.

The step of exchanging a frame of data with the base station may includeexchanging the frame via a channel having a bandwidth of one of 5, 10and 20 Mhz.

The step of exchanging a frame of data with the base station may includeforming the frame from data received from a data buffer within themobile communication terminal.

The step of exchanging a frame of data with the base station may includedecomposing the frame into data to be stored in a data buffer within themobile communication terminal.

A number of the plurality of first subframes and a number of theplurality of second subframes may be predetermined, or may be determinedbased upon an instruction received from the base station.

The frame may have a cyclic prefix (CP) length of 1/16 useful symboltime (Tu).

The first number of OFDMA symbols may be seven symbols and the secondnumber of OFDMA symbols may be 6 symbols.

The step of exchanging may include time division duplexing (TDD) theframe with another frame.

The plurality of first subframes may include 2 first subframes and theplurality of second subframes may include 6 second subframes.

One of the 6 second subframes may include an idle symbol.

The frame may include one first subframe followed by 6 second subframesfollowed by another first subframe.

A 4^(th) of the six second subframes may include an idle symbol.

The idle symbol may be a sixth symbol of the 4^(th) second subframe.

The frame may include a plurality of downlink subframes followed by aplurality of uplink subframes.

The plurality of downlink subframes may include at least one of theplurality of first subframes and at least one of the plurality of secondsubframes, and the plurality of uplink subframes may include at leastone other of the plurality of first subframes and at least one other ofthe plurality of second subframes.

A ratio between the plurality of uplink subframes and the plurality ofdownlink subframes may be one of 4:4, 6:2, 7:1, and 5:3.

The frame may include a transmit/receive transition gap (TTG) betweenthe plurality of uplink subframes and the plurality of downlinksubframes.

The step of exchanging may include frequency division duplexing (FDD)the frame with another frame.

The plurality of first subframes may include 3 first subframes and theplurality of second subframes may include 5 second subframes.

The frame may include one first subframe followed by 3 second subframesfollowed by a second first subframe followed by 2 second subframesfollowed by a third first subframe.

In another aspect of the invention, there is a mobile communicationterminal configured to communicate with a base station. The mobilecommunication terminal includes a display; a transceiver; and aprocessor operatively connected to the display and transceiver, theprocessor configured to exchange a frame of data with the base station.The frame of data includes a) a plurality of first subframes each havinga first number of orthogonal frequency division multiple access (OFDMA)symbols, and b) a plurality of second subframes each having a secondnumber of orthogonal frequency division multiple access (OFDMA) symbolsdifferent from the first number. A first and a last subframe eachcomprises one of the plurality of first subframes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows an example of a frame structure.

FIG. 3 shows an example of a frame hierarchy.

FIG. 4 shows an example of a conventional time division duplexing (TDD)frame structure having a cyclic prefix (CP) length of ⅛ useful symboltime (Tu) when a downlink-to-uplink ratio (DL/UL ratio) is 4:4.

FIG. 5 shows an example of a conventional TDD frame structure having aCP length of ⅛ Tu when a DL/UL ratio is 5:3.

FIG. 6 shows an example of a conventional TDD frame structure having aCP length of ⅛ Tu when a DL/UL ratio is 6:2.

FIG. 7 shows an example of a conventional TDD frame structure having aCP length of ⅛ Tu when a DL/UL ratio is 7:1.

FIG. 8 shows an example of a conventional frequency division duplexing(FDD) frame structure having a CP length of ⅛ Tu.

FIG. 9 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu with a CP length of ⅛ Tu and when a DL/UL ratio is 4:4according to an embodiment of the present invention.

FIG. 10 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu with a CP length of ⅛ Tu and when a DL/UL ratio is 5:3according to an embodiment of the present invention.

FIG. 11 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu with a CP length of ⅛ Tu and when a DL/UL ratio is 6:2according to an embodiment of the present invention.

FIG. 12 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu with a CP length of ⅛ Tu and when a DL/UL ratio is 7:1according to an embodiment of the present invention.

FIG. 13 shows TDD frame structures having a CP length of ¼ Tu and FDDframe structures having a common feature with the TDD frame structuresaccording to an embodiment of the present invention.

FIG. 14 shows TDD frames having a CP length of ¼ Tu and including a basesubframe constructed of a subframe type-2 (SFT-2) subframe and FDDframes having a common feature with the TDD frame according to anembodiment of the present invention.

FIG. 15 shows TDD frame structures having a CP length of 1/16 Tu and FDDframe structures having a common feature with the TDD frame structuresaccording to an embodiment of the present invention.

FIG. 16 shows TDD frame structures having a CP length of 1/32 Tu and FDDframe structures having a common feature with the TDD frame structuresaccording to an embodiment of the present invention.

FIG. 17 is a block diagram showing an apparatus of wirelesscommunication.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system. The wireless communicationsystem can be widely deployed to provide a variety of communicationservices, such as voices, packet data, etc.

Referring to FIG. 1, the wireless communication system includes a basestation (BS) 20 and at least one user equipment (UE) 10. The UE 10 maybe fixed or mobile, and may be referred to as another terminology, suchas a mobile station (MS), a user terminal (UT), a subscriber station(SS), a wireless device, etc. The BS 20 is generally a fixed stationthat communicates with the UE 10 and may be referred to as anotherterminology, such as a node-B, a base transceiver system (BTS), anaccess point, etc. There are one or more cells within the coverage ofthe BS 20.

Hereinafter, a downlink denotes a communication link from the BS 20 tothe UE 10, and an uplink denotes a communication link from the UE 10 tothe BS 20. In downlink, a transmitter may be a part of the BS 20, and areceiver may be a part of the UE 10. In uplink, the transmitter may be apart of the UE 10, and the receiver may be a part of the BS 20.

The wireless communication system may be a system based on orthogonalfrequency division multiplexing (OFDM)/orthogonal frequency divisionmultiple access (OFDMA). The OFDM uses a plurality of orthogonalsubcarriers. The OFDM uses orthogonality between an inverse fast Fouriertransform (IFFT) and a fast Fourier transform (FFT). The transmittertransmits data by performing the IFFT. The receiver restores originaldata by performing the FFT on a received signal. The transmitter usesthe IFFT to combine the plurality of subcarriers. The receiver uses theFFT to separate the plurality of subcarriers.

FIG. 2 shows an example of a frame structure. A frame is a data sequenceused according to a physical specification in a fixed time duration.This may be found in section 8.4.4.2 of “Part 16: Air Interface forFixed Broadband Wireless Access Systems” in the institute of electricaland electronics engineers (IEEE) standard 802.16-2004, the entirecontents of which is incorporated herein by reference.

Referring to FIG. 2, the frame includes a downlink (DL) frame and anuplink (UL) frame. In a time division duplexing (TDD) scheme, UL and DLtransmissions are achieved at different time points but share the samefrequency band. The DL frame temporally precedes the UL frame. The DLframe sequentially includes a preamble, a frame control header (FCH), aDL-MAP, a UL-MAP, and a burst region. Guard times are provided toidentify the UL frame and the DL frame and are inserted to a middleportion (between the DL frame and the UL frame) and a last portion (nextto the UL frame) of the frame. A transmit/receive transition gap (TTG)is a gap between a downlink burst and a subsequent uplink burst. Areceive/transmit transition gap (RTG) is a gap between an uplink burstand a subsequent downlink burst.

The preamble is used between a BS and a UE for initial synchronization,cell search, and frequency-offset and channel estimation. The FCHincludes information on a length of a DL-MAP message and a coding schemeof the DL-MAP.

The DL-MAP is a region for transmitting the DL-MAP message. The DL-MAPmessage defines access to a DL channel. The DL-MAP message includes aconfiguration change count of a downlink channel descriptor (DCD) and aBS identifier (ID). The DCD describes a downlink burst profile appliedto a current MAP. The downlink burst profile indicates characteristicsof a DL physical channel. The DCD is periodically transmitted by the BSby using a DCD message.

The UL-MAP is a region for transmitting a UL-MAP message. The UL-MAPmessage defines access to a UL channel. The UL-MAP message includes aconfiguration change count of an uplink channel descriptor (UCD) andalso includes an effective start time of uplink allocation defined bythe UL-MAP. The UCD describes an uplink burst profile. The uplink burstprofile indicates characteristics of a UL physical channel and isperiodically transmitted by the BS by using a UCD message.

FIG. 3 shows an example of a frame hierarchy.

Referring to FIG. 3, a superframe is divided into four radio frames(hereinafter, frames) each having the same size. The superframe mayinclude a superframe header. The superframe header may be assigned to afirst frame among a plurality of frames constituting the superframe. Acommon control channel may be allocated to the superframe header. Thecommon control channel is used to transmit information regarding theframes constituting the superframe or control information (e.g., systeminformation) that can be commonly used by all UEs. The systeminformation is necessary information which must be known to performcommunication between a UE and a BS. The BS periodically transmits thesystem information. The system information may be periodicallytransmitted in every 20 to 40 milliseconds (ms). A size of thesuperframe can be determined by considering a transmission period of thesystem information. Although a size of each superframe is 20 ms and asize of each frame is 5 ms in FIG. 3, this is for exemplary purposesonly, and thus the present invention is not limited thereto.

One frame consists of 8 subframes. One subframe can be allocated foruplink or downlink transmission. Each subframe for downlink transmissionmay include a signal for resource allocation. For example, the subframemay include 6 OFDM symbols. This is for exemplary purposes only, andthus the present invention is not limited thereto.

Now, a TDD frame structure and an FDD frame structure satisfyingbackward compatibility with a legacy system will be described. A TDDframe is a frame in which the entire frequency band is used for uplinkor downlink transmission. Uplink and downlink regions are separated in atime domain. An FDD frame is a frame in which the uplink transmissionand the downlink transmission occupy different frequency bands and aresimultaneously achieved. A dual frame is a frame that satisfies backwardcompatibility with the legacy system. The dual frame includes a resourceregion that supports the legacy system and a resource region thatsupports a new/evolved system. The legacy system may be the institute ofelectrical and electronics engineers (IEEE) 802.16e system. The newsystem may be the IEEE 802.16m system. The terms used in the IEEE802.16e frame structure described in FIG. 2 may be equally defined inthe IEEE 802.16m frame structure without modification or with minormodifications.

Table 1 below shows frame parameters.

TABLE 1 Transmission Bandwidth (MHz) 5 10 20 Over Sampling Factor 28/25Sampling Frequency (MHz) 5.6 11.2 22.4 FFT Size 512 1024 2048 SubcarrierSpacing (KHz) 10.94 OFDM Symbol Time, Tu (μs) 91.4 Cyclic Prefix (CP) Ts(ps) OFDM Symbols per Frame Idle Time (p) no legacy support Tg = ¼Tu91.4 + 22.85 = 114.25 43 87.25 legacy support Tg = ⅛Tu 91.4 + 11.42 =102.82 48 64.64 no legacy support Tg = 1/16Tu 91.4 + 5.71 = 97.11 5147.39 no legacy support Tg = 1/32Tu 91.4 + 2.86 = 94.26 53 4.22

To satisfy backward compatibility with the frame of the legacy system(i.e., IEEE 802.16e system), parameters (e.g., a transmission bandwidth,a sampling frequency, an FFT size, a subcarrier spacing, etc.) of thenew system may conform to IEEE 802.16e frame parameters. In aconventional legacy system mode supporting IEEE 802.16e, a cyclic prefix(CP) length can be set to ⅛ useful symbol time (Tu) and one frame caninclude 48 OFDM symbols. In a conventional legacy support disabled modenot supporting the legacy system, new CP lengths can be set to ¼ Tu,1/16 Tu, and 1/32 Tu and one frame can include 43, 51, and 53 OFDMsymbols respectively for the new CP lengths. For example, when onesubframe consists of 6 OFDM symbols, a frame with a CP length of ¼ Tumay consist of 7 subframes and one residual OFDM symbol, a frame with aCP length of 1/16 Tu may consist of 8 subframes and three residual OFDMsymbols, and a frame with a CP length of 1/32 Tu may consist of 8subframes and 5 residual OFDM symbols.

A CP is a copy of a final useful symbol period Tg, and can be expressedby a ratio with respect to a useful symbol time (Tu).

Table 2 below shows lengths of a TTG and an RTG in a TDD structureaccording to the IEEE 802.16e standard. The TTG can be expressedhereinafter in other terms such as a switching point, an idle frame,etc. This is for exemplary purposes only, and thus the present inventionis not limited thereto. The switching points of the new system may be alonger or shorter than those in the IEEE 802.16e standard.

TABLE 2 Bandwidth 5M 10M 8.75M 7M 14M PS (ns)(=4/Fs) 714.286 357.142 400500 250 TTG (.ts) 148PS = 105.71 296PS = 105.71 218PS = 87.2 376PS = 188752PS = 188 RTG (μs) 84PS = 60.00 168PS = 60.00 186PS = 74.4 120PS = 60240PS = 60 TTG:RTG 1.76:1 1.76:1 1.17:1 3.13:1 3.13:1

FIG. 4 to FIG. 7 show examples of a TDD frame structure having a CPlength of ⅛ Tu when a downlink-to-uplink ratio (DL/UL ratio) is 4:4(FIG. 4), 5:3 (FIG. 5), 6:2 (FIG. 6), or 7:1 (FIG. 7).

Referring to FIG. 4 to FIG. 7, a new TDD frame satisfying backwardcompatibility is based on the conventional TDD frame structure and basedon the aforementioned parameters and values of Table 1 and Table 2above. That is, the new TDD frame has a length of 5 ms, a CP length of ⅛Tu, and a bandwidth of 10 megahertz (MHz). Further, the new TDD frameincludes 48 OFDM symbols. In addition, basic control information (e.g.,preamble, FCH, and MAP) can be defined according to the IEEE 802.16estandard. The TTG length and the RTG length are the same as shown inTable 2 above.

In FIG. 4 to FIG. 7, one TDD frame consists of 8 subframes. A subframeis a basic unit of data allocation and scheduling, and generallyconsists of 6 OFDM symbols. Herein, the number 6 is determined byconsidering a bandwidth in a time axis and a pilot allocation pattern.In this case, a radio channel property is considered together with asize of data which is allocated through coding and modulation of mediaaccess control (MAC) and physical (PHY) entities. When one subframe isconstructed of 6 OFDM symbols, a DL/UL ratio can be effectivelyconfigured, the number of OFDM symbols in a UL duration can be set to amultiple of 3 in a dual frame, and data delay capability can beimproved. However, the number of OFDM symbols constituting one subframeis not limited thereto.

A TTG is located between a DL region and a UL region. An RTG is locatedbetween the UL region and a subsequent frame. An idle time may beincluded in the TTG or the RTG according to a CP length.

Specifically, referring to FIG. 4, a DL duration is a time periodbetween a start point of a frame and a time point of 2364.86microseconds (μs), and includes 23 OFDM symbols with a CP length of ⅛Tu. A TTG duration is a time period between the time point of 2364.86 psand a time point of 2472.32 its, and thus includes a time period of107.46 prs corresponding to a portion of the idle time and the TTGduration of Table. 2. A UL duration is a time period between the timepoint of 2472.32 pis and a time point of 4940 gs, and includes 24 OFDMsymbols with a CP length of ⅛ Tu. An RTG duration is a time periodbetween the time point of 4940 Rs and an end point of the frame, andthus includes a time period of 60 ps corresponding to the RTG durationof Table 2.

Referring to FIG. 5, a DL duration is a time period between a startpoint of a frame and a time point of 2981.78 μs, and includes 29 OFDMsymbols with a CP length of ⅛ Tu. A TTG duration is a time periodbetween the time point of 2981.78 i.ts and a time point of 3089.24 p,s,and thus includes a time period of 107.46 !is corresponding to a portionof the idle time and the TTG duration of Table. 2. A UL duration is atime period between the time point of 3089.24 ps and a time point of4940 μs, and includes 18 OFDM symbols with a CP length of ⅛ Tu. An RTGduration is a time period between the time point of 4940 pis and an endpoint of the frame, and thus includes a time period of 60 pscorresponding to the RTG duration of Table 2.

Referring to FIG. 6, a DL duration is a time period between a startpoint of a frame and a time point of 3598.7 ms, and includes 35 OFDMsymbols with a CP length of ⅛ Tu. A TTG duration is a time periodbetween the time point of 3598.7 gs and a time point of 3706.16 μs, andthus includes a time period of 107.46 i.ts corresponding to a portion ofthe idle time and the TTG duration of Table. 2. A UL duration is a timeperiod between the time point of 3706.16 is and a time point of 4940 μs,and includes 12 OFDM symbols with a CP length of ⅛ Tu. An RTG durationis a time period between the time point of 4940 tts and an end point ofthe frame, and thus includes a time period of 60 i.ts corresponding tothe RTG duration of Table 2.

Referring to FIG. 7, a DL duration is a time period between a startpoint of a frame and a time point of 4215.62 pts, and includes 41 OFDMsymbols with a CP length of ⅛ Tu. A TTG duration is a time periodbetween the time point of 4215.62 gs and a time point of 4323.08 1.1,s,and thus includes a time period of 107.46 ps corresponding to a portionof the idle time and the TTG duration of Table. 2. A UL duration is atime period between the time point of 4323.08 ps and a time point of4940 ′,is, and includes 6 OFDM symbols with a CP length of ⅛ Tu. An RTGduration is a time period between the time point of 4940 pis and an endpoint of the frame, and thus includes a time period of 60 μscorresponding to the RTG duration of Table 2.

In FIG. 4 to FIG. 7, the RTG is set to 60.0 Rs, and the TTG is set to107.46 tts by allowing most of idle time to belong to the TTG. However,as shown in Table 2 above, it is also possible to set the TTG to 105.71μs and the RTG to 61.77 Its by allowing most of idle time to belong tothe RTG.

FIG. 8 shows an example of an FDD frame structure having a CP length of⅛ Tu.

Referring to FIG. 8, 48 OFDM symbols are included in one frame when atotal frame length is 5 ms. One frame consists of 8 subframes. Onesubframe consists of 6 OFDM symbols. The idle time at the end of theframe is 64.64 pis as shown in Table 1 above.

The TDD and FDD frame structures shown in FIG. 4 to FIG. 8 have a CPlength of ⅛ Tu. However, when a TDD frame structure having a differentCP length coexists in an adjacent cell, mutual interference frommis-alignment between DL and UL transmissions may occur in datatransmission. The present invention provides a TDD frame structure, inwhich TDD frames have various CP lengths to prevent mutual interferencewith a TDD frame having a CP length of ⅛ Tu, and also provides an FDDframe structure having a common feature with the TDD frame structure.

<Frame Structure in which Switching Points Overlap Between Frames HavingDifferent CP Lengths>

FIG. 9 shows a TDD frame structure having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu when a DL/UL ratio is 4:4 according to an embodiment of thepresent invention.

Referring to FIG. 9, a reference frame has the same conventionalstructure of FIG. 4. That is, the frame has a total length of 5 ms and aCP length of ⅛ Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is ¼ Tu.A total frame length is 5 ms. A DL duration is a time period between astart point of a frame and a time point of 2399.25 ps, and includes 21OFDM symbols with a CP length of ¼ Tu. A TTG duration is a time periodbetween the time point of 2399.25 μs and a time point of 2540.75 tts,and thus includes a time period of 141.5 pis corresponding to a portionof the idle time and the TTG duration of Table. 2. A UL duration is atime period between the time point of 2540.75 ps and a time point of4940 is, and includes 21 OFDM symbols with a CP length of ¼ Tu. An RTGduration is a time period between the time point of 4940 p.s and an endpoint of the frame, and thus includes a time period of 60 luscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 5 OFDM symbols, one residual OFDM symbol isfurther allocated to the DL duration, one residual OFDM symbol isfurther allocated to the UL duration, and the remaining one residualOFDM symbol is allocated between the TTG and RTG durations. In otherwords, the last DL subframe is constructed of 6 OFDM symbols in FDD, andthe last symbol in this subframe is punctured and is converted to asubframe of 5 OFDM symbols in TDD due to the TTG duration. In the firstTDD frame structure of FIG. 9, a first subframe of the DL duration and alast subframe of the UL duration are constructed of 6 OFDM symbols.However, any one subframe belonging to the DL duration can beconstructed of 6 OFDM symbols instead of the first subframe, and any onesubframe belonging to the UL duration can be constructed of 6 OFDMsymbols instead of the last subframe. In addition, the DL duration canbe constructed of a plurality of subframes consisting of 5 OFDM symbolsand the remaining one independent OFDM symbol, and the UL duration canbe constructed of a plurality of subframes consisting of 5 OFDM symbolsand the remaining one independent OFDM symbol. Such a subframe structureis for exemplary purposes only. That is, the subframes belonging to theDL duration can be constructed of any number of OFDM symbols, and thesubframes belonging to the UL duration can be constructed of any numberof OFDM symbols, wherein the subframes can have different sizes.

In a second TDD frame structure of this embodiment, a CP length is 1/16Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 2427.8 μs, and includes 25OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a timeperiod between the time point of 2427.8 Rs and a time point of 2511.6Rs, and thus includes a time period of 84.5 Rs corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 2511.6 is and a time point of4940 Rs, and includes 25 OFDM symbols with a CP length of 1/16 Tu. AnRTG duration is a time period between the time point of 4940 Rs and anend point of the frame, and thus includes a time period of 60 Rscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, three residual OFDM symbolsremain. Among the three residual OFDM symbols, one OFDM symbol isfurther allocated to the DL duration, one OFDM symbol is furtherallocated to the UL duration, and the remaining one OFDM symbol isallocated between the TTG and RTG durations. In other words, the last DLsubframe is constructed of 7 OFDM symbols in FDD, and the last symbol inthis subframe is punctured and is converted to a subframe of 6 OFDMsymbols in TDD due to the TTG duration. In the second TDD framestructure of FIG. 9, a first subframe of the DL duration is constructedof 7 OFDM symbols and a last subframe of the UL duration is constructedof 7 OFDM symbols. However, any one subframe belonging to the DLduration can be constructed of 7 OFDM symbols instead of the firstsubframe, and any one subframe belonging to the UL duration can beconstructed of 7 OFDM symbols instead of the last subframe. In addition,the DL duration can be constructed of a plurality of subframesconsisting of 6 OFDM symbols and the remaining one independent OFDMsymbol, and the UL duration can be constructed of a plurality ofsubframes consisting of 6 OFDM symbols and the remaining one independentOFDM symbol. Such a subframe structure is for exemplary purposes only.That is, the subframes belonging to the DL duration can be constructedof any number of OFDM symbols, and the subframes belonging to the ULduration can be constructed of any number of OFDM symbols, wherein thesubframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 2450.76 pts, and includes26 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a timeperiod between the time point of 2450.76 tis and a time point of 2583.5μs, and thus includes a time period of 132.42 ps corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 2583.5 gs and a time point of4940 μs, and includes 25 OFDM symbols with a CP length of 1/32 Tu. AnRTG duration is a time period between the time point of 4940 i.ts and anend point of the frame, and thus includes a time period of 60 1.tscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, 5 residual OFDM symbolsremain. Among the 5 residual OFDM symbol, two OFDM symbols are furtherallocated to the DL duration, one OFDM symbol is further allocated tothe UL duration, and the remaining two OFDM symbols are allocatedbetween the TTG and RTG durations. In the third TDD frame structure ofFIG. 9, a first subframe and a last subframe of the DL duration areconstructed of 7 OFDM symbols and a last subframe of the UL duration isconstructed of 7 OFDM symbols. However, any two subframes belonging tothe DL duration can be constructed of 7 OFDM symbols instead of thefirst and last DL subframes, and any one subframe belonging to the ULduration can be constructed of 7 OFDM symbols instead of the last ULsubframe. In addition, the DL duration can be constructed of a pluralityof subframes consisting of 6 OFDM symbols and the remaining twoindependent OFDM symbols, and the UL duration can be constructed of aplurality of subframes consisting of 6 OFDM symbols and the remainingone independent OFDM symbol. Such a subframe structure is for exemplarypurposes only. That is, the subframes belonging to the DL duration canbe constructed of any number of OFDM symbols, and the subframesbelonging to the UL duration can be constructed of any number of OFDMsymbols, wherein the subframes can have different sizes.

When the TDD frame is configured as shown in FIG. 9, mutual interferencedoes not occur even if the frame structures having different CP lengthsexist in adjacent cells. That is, mutual interference does not occurbecause a DL duration of a frame having a CP length of ⅛ Tu does notoverlap with a UL duration of a frame having a CP length of ¼ Tu, 1/16Tu, or 1/32 Tu, and a UL duration of a frame having a CP length of ⅛ Tudoes not overlap with a DL duration of a frame having a CP length of ¼Tu, 1/16 Tu, or 1/32 Tu.

FIG. 10 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu when a DL/UL ratio is 5:3 with a CP length of ⅛ Tu accordingto an embodiment of the present invention.

Referring to FIG. 10, a reference frame has the same conventionalstructure of FIG. 5. That is, the frame has a total length of 5 ms and aCP length of ⅛ Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is ¼ Tu.A total frame length is 5 ms. A DL duration is a time period between astart point of a frame and a time point of 2856.25 i.ts, and includes 25OFDM symbols with a CP length of ¼ Tu. A TTG duration is a time periodbetween the time point of 2856.25 is and a time point of 2997.75 is, andthus includes a time period of 141.5 pts corresponding to a portion ofthe idle time and the TTG duration of Table. 2. A UL duration is a timeperiod between the time point of 2997.75 tis and a time point of 4940tts, and includes 17 OFDM symbols with a CP length of ¼ Tu. An RTGduration is a time period between the time point of 4940 μs and an endpoint of the frame, and thus includes a time period of 60 lascorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, one residual OFDM symbol isfurther allocated to the DL duration, a first subframe of the ULduration is constructed of 5 OFDM symbols, and one OFDM symbol precedingthe first subframe of the UL duration is punctured. In the first TDDframe structure of FIG. 10, a first subframe of the DL duration isconstructed of 7 OFDM symbols. However, any one subframe belonging tothe DL duration can be constructed of 7 OFDM symbols instead of thefirst subframe. In addition, the DL duration can be constructed of aplurality of subframes consisting of 6 OFDM symbols and the remainingone independent OFDM symbol. Such a subframe structure is for exemplarypurposes only. That is, the subframes belonging to the DL duration canbe constructed of any number of OFDM symbols, and the subframesbelonging to the UL duration can be constructed of any number of OFDMsymbols, wherein the subframes can have different sizes.

Alternatively, in the TDD frame structure having a CP length of ¼ Tu, ifone subframe is constructed of 5 OFDM symbols, one residual OFDM symbolcan be further allocated to the DL duration, one residual OFDM symbolcan be further allocated to the UL duration, and the remaining oneresidual OFDM symbol can be allocated to the TTG duration. Thisalternative method is the same as the case of ¼ Tu, which was explainedwith a DL to UL ratio of 4:4 in FIG. 9.

In a second TDD frame structure of this embodiment, a CP length is 1/16Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 3010.41 ps, and includes 31OFDM symbols with a CP length of 1/16 Tu. A TM duration is a time periodbetween the time point of 3010.41 i.ts and a time point of 3094.91 tis,and thus includes a time period of 84.5 tts corresponding to a portionof the idle time and the TTG duration of Table. 2. A UL duration is atime period between the time point of 3094.91 pts and a time point of4940 μs, and includes 19 OFDM symbols with a CP length of 1/16 Tu. AnRTG duration is a time period between the time point of 4940 ils and anend point of the frame, and thus includes a time period of 60 pscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, three residual OFDM symbolsremain. Among the three residual OFDM symbols, one OFDM symbol isfurther allocated to the DL duration, one OFDM symbol is furtherallocated to the UL duration, and the remaining one OFDM symbol isallocated between the TTG and RTG durations. In other words, the last DLsubframe is constructed of 7 OFDM symbols in FDD, and the last symbol inthis subframe is punctured and is converted to a subframe of 6 OFDMsymbols in TDD due to the TTG duration. This may be considered an idlesymbol. In the second TDD frame structure of FIG. 10, a first subframeof the DL duration is constructed of 7 OFDM symbols and a last subframeof the UL duration is constructed of 7 OFDM symbols. However, any onesubframe belonging to the DL duration can be constructed of 7 OFDMsymbols instead of the first subframe, and any one subframe belonging tothe UL duration can be constructed of 7 OFDM symbols instead of the lastsubframe. In addition, the DL duration can be constructed of a pluralityof subframes consisting of 6 OFDM symbols and the remaining oneindependent OFDM symbol, and the UL duration can be constructed of aplurality of subframes consisting of 6 OFDM symbols and the remainingone independent OFDM symbol. The remaining one independent OFDM mayfollow a subframe consisting of 6 OFDM symbols, or may be a symbol of asubframe consisting of 7 OFDM symbols (e.g., a seventh, or last,symbol). Such a subframe structure is for exemplary purposes only. Thatis, the subframes belonging to the DL duration can be constructed of anynumber of OFDM symbols, and the subframes belonging to the UL durationcan be constructed of any number of OFDM symbols, wherein the subframescan have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 3016.32 Its, and includes32 OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a timeperiod between the time point of 3016.32 ps and a time point of 3054.80pis, and thus includes a time period of 38.48 ps corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 3054.80 ps and a time pointof 4940 and includes 20 OFDM symbols with a CP length of 1/32 Tu. An RTGduration is a time period between the time point of 4940 ps and an endpoint of the frame, and thus includes a time period of 60 pscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, 5 residual OFDM symbolsremain. Among the 5 residual OFDM symbols, two OFDM symbols are furtherallocated to the DL duration, two OFDM symbols are further allocated tothe UL duration, and the remaining one OFDM symbol is allocated betweenthe TTG and RTG durations. In the third TDD frame structure of FIG. 10,a first subframe and a last subframe of the DL duration are constructedof 7 OFDM symbols and a first subframe and a last subframe of the ULduration are constructed of 7 OFDM symbols. However, any two subframesbelonging to the DL duration can be constructed of 7 OFDM symbolsinstead of the first and last DL subframes, and any two subframesbelonging to the UL duration can be constructed of 7 OFDM symbolsinstead of the first and the last UL subframes. In addition, the DLduration can be constructed of a plurality of subframes consisting of 6OFDM symbols and the remaining two independent OFDM symbols, and the ULduration can be constructed of a plurality of subframes consisting of 6OFDM symbols and the remaining two independent OFDM symbols. Such asubframe structure is for exemplary purposes only. That is, thesubframes belonging to the DL duration can be constructed of any numberof OFDM symbols, and the subframes belonging to the UL duration can beconstructed of any number of OFDM symbols, wherein the subframes canhave different sizes.

If the TTG duration requires a longer duration than 38.48 μs, one ofOFDM symbols additionally allocated to the DL duration or the ULduration can be further allocated for the TTG duration. For example, oneof OFDM symbols additionally allocated to the UL duration can be furtherallocated for the TTG duration, and thus the TTG duration may be 132.74ps.

When the TDD frame is configured as shown in FIG. 10, mutualinterference does not occur even if the frame structures havingdifferent CP lengths exist in adjacent cells. That is, mutualinterference does not occur since a DL duration of a frame having a CPlength of ⅛ Tu does not overlap with a UL duration of a frame having aCP length of ¼ Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a framehaving a CP length of ⅛ Tu does not overlap with a DL duration of aframe having a CP length of ¼ Tu, 1/16 Tu, or 1/32 Tu.

FIG. 11 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu with a CP length of ⅛ Tu and when a DL/UL ratio is 6:2according to an embodiment of the present invention.

Referring to FIG. 11, a reference frame has the same conventionalstructure of FIG. 6. That is, the frame has a total length of 5 ms and aCP length of ⅛ Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is ¼ Tu.A total frame length is 5 ms. A DL duration is a time period between astart point of a frame and a time point of 3541.8 μs, and includes 31OFDM symbols with a CP length of ¼ Tu. A TTG duration is a time periodbetween the time point of 3541.8 μs and a time point of 3683.25 p.s, andthus includes a time period of 141.45 Its corresponding to a portion ofthe idle time and the TTG duration of Table. 2. A UL duration is a timeperiod between the time point of 3683.25 ps and a time point of 4940 Rs,and includes 11 OFDM symbols with a CP length of ¼ Tu. An RTG durationis a time period between the time point of 4940 gs and an end point ofthe frame, and thus includes a time period of 60 is corresponding to theRTG duration of Table 2. The time points may be varied according to theTTG and RTG durations. Accordingly, if one subframe is constructed of 6OFDM symbols, one residual OFDM symbol is further allocated to the DLduration, a first subframe of the UL duration is constructed of 5 OFDMsymbols, and one OFDM symbol preceding the first subframe of the ULduration is punctured. In the first TDD frame structure of FIG. 11, afirst subframe of the DL duration is constructed of 7 OFDM symbols.However, any one subframe belonging to the DL duration can beconstructed of 7 OFDM symbols instead of the first subframe. Inaddition, the DL duration can be constructed of a plurality of subframesconsisting of 6 OFDM symbols and the remaining one independent OFDMsymbol. Such a subframe structure is for exemplary purposes only. Thatis, the subframes belonging to the DL duration can be constructed of anynumber of OFDM symbols, and the subframes belonging to the UL durationcan be constructed of any number of OFDM symbols, wherein the subframescan have different sizes.

Alternatively, in the TDD frame structure having a CP length of ¼ Tu, ifone subframe is constructed of 5 OFDM symbols, one residual OFDM symbolcan be further allocated to the DL duration, one residual OFDM symbolcan be further allocated to the UL duration, and the remaining one OFDMsymbol can be allocated to the TTG duration. This alternative method isthe same as the case of ¼ Tu, which was explained with a DL to UL ratioof 4:4 in FIG. 9.

In a second TDD frame structure of this embodiment, a CP length is 1/16Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 3593.07 is, and includes 37OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a timeperiod between the time point of 3593.07 As and a time point of 3677.57gs, and thus includes a time period of 84.5 gs corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 3677.57 ps and a time pointof 4940 las, and includes 13 OFDM symbols with a CP length of 1/16 Tu.An RTG duration is a time period between the time point of 4940 ps andan end point of the frame, and thus includes a time period of 60 Itscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, three residual OFDM symbolsremain. Among the three residual OFDM symbols, one OFDM symbol isfurther allocated to the DL duration, one OFDM symbol is furtherallocated to the UL duration, and the remaining one OFDM symbol isallocated between the TTG and RTG durations. In other words, the last DLsubframe is constructed of 7 OFDM symbols in FDD, and the last symbol inthis subframe is punctured and is converted to a subframe of 6 OFDMsymbols in TDD due to the TTG duration. In the second TDD framestructure of FIG. 11, a first subframe of the DL duration is constructedof 7 OFDM symbols and a last subframe of the UL duration is constructedof 7 OFDM symbols. However, any one subframe belonging to the DLduration can be constructed of 7 OFDM symbols instead of the firstsubframe, and any one subframe belonging to the UL duration can beconstructed of 7 OFDM symbols instead of the last subframe. In addition,the DL duration can be constructed of a plurality of subframesconsisting of 6 OFDM symbols and the remaining one independent OFDMsymbol, and the UL duration can be constructed of a plurality ofsubframes consisting of 6 OFDM symbols and the remaining one independentOFDM symbol. Such a subframe structure is for exemplary purposes only.That is, the subframes belonging to the DL duration can be constructedof any number of OFDM symbols, and the subframes belonging to the ULduration can be constructed of any number of OFDM symbols, wherein thesubframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 3581.88 μs, and includes 38OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a timeperiod between the time point of 3581.88 μs and a time point of 3620.36its, and thus includes a time period of 38.48 las corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 3620.36 Its and a time pointof 4940 μs, and includes 14 OFDM symbols with a CP length of 1/32 Tu. AnRTG duration is a time period between the time point of 4940 1.ts and anend point of the frame, and thus includes a time period of 60 !iscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, 5 residual OFDM symbolsremain. Among the 5 residual OFDM symbols, two OFDM symbols are furtherallocated to the DL duration, two OFDM symbols are further allocated tothe UL duration, and the remaining one OFDM symbol is allocated betweenthe TTG and RTG durations. In the third TDD frame structure of FIG. 11,a first subframe and a last subframe of the DL duration are constructedof 7 OFDM symbols. However, any two subframes belonging to the DLduration can be constructed of 7 OFDM symbols instead of the first andlast DL subframes. In addition, the DL duration can be constructed of aplurality of subframes consisting of 6 OFDM symbols and the remainingtwo independent OFDM symbols, and the UL duration can be constructed ofa plurality of subframes consisting of 6 OFDM symbols and the remainingtwo independent OFDM symbols. Such a subframe structure is for exemplarypurposes only. That is, the subframes belonging to the DL duration canbe constructed of any number of OFDM symbols, and the subframesbelonging to the UL duration can be constructed of any number of OFDMsymbols, wherein the subframes can have different sizes.

If the TTG duration requires a longer duration than 38.48 μs, one ofOFDM symbols additionally allocated to the DL duration or the ULduration can be further allocated for the TTG duration. For example, oneof OFDM symbols additionally allocated to the UL duration can be furtherallocated for the TTG duration, and thus the TTG duration may be 132.74Rs.

When the TDD frame is configured as shown in FIG. 11, mutualinterference does not occur even if the frame structures havingdifferent CP lengths exist in adjacent cells. That is, mutualinterference does not occur since a DL duration of a frame having a CPlength of ⅛ Tu does not overlap with a UL duration of a frame having aCP length of ¼ Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a framehaving a CP length of ⅛ Tu does not overlap with a DL duration of aframe having a CP length of ¼ Tu, 1/16 Tu, or 1/32 Tu.

FIG. 12 shows TDD frame structures having a CP length of ¼ Tu, 1/16 Tu,or 1/32 Tu with a CP length of ⅛ Tu and when a DL/UL ratio is 7:1according to an embodiment of the present invention.

Referring to FIG. 12, a reference frame has the same conventionalstructure of FIG. 7. That is, the frame has a total length of 5 ms and aCP length of ⅛ Tu, and includes 8 subframes.

In a first TDD frame structure of this embodiment, a CP length is ¼ Tu.A total frame length is 5 ms. A DL duration is a time period between astart point of a frame and a time point of 4227.25 Its, and includes 37OFDM symbols with a CP length of ¼ Tu. A TTG duration is a time periodbetween the time point of 4227.25 Rs and a time point of 4368.75 Rs, andthus includes a time period of 141.5 Rs corresponding to a portion ofthe idle time and the TTG duration of Table. 2. A UL duration is a timeperiod between the time point of 4368.75 Rs and a time point of 4940 ps,and includes 5 OFDM symbols with a CP length of ¼ Tu. An RTG duration isa time period between the time point of 4940 Rs and an end point of theframe, and thus includes a time period of 60 Rs corresponding to the RTGduration of Table 2. The time points may be varied according to the TTGand RTG durations. Accordingly, if one subframe is constructed of 6 OFDMsymbols, one residual OFDM symbol is further allocated to the DLduration, a first subframe of the UL duration is constructed of 5 OFDMsymbols, and one OFDM symbol preceding the first subframe of the ULduration is punctured. In the first TDD frame structure of FIG. 12, afirst subframe of the DL duration is constructed of 7 OFDM symbols.However, any one subframe belonging to the DL duration can beconstructed of 7 OFDM symbols. instead of the first subframe Inaddition, the DL duration can be constructed of a plurality of subframesconsisting of 6 OFDM symbols and the remaining one independent OFDMsymbol. Such a subframe structure is for exemplary purposes only. Thatis, the subframes belonging to the DL duration can be constructed of anynumber of OFDM symbols, and the subframes belonging to the UL durationcan be constructed of any number of OFDM symbols, wherein the subframescan have different sizes.

Alternatively, in the TDD frame structure having a CP length of ¼ Tu, ifone subframe is constructed of 5 OFDM symbols, one residual OFDM symbolcan be further allocated to the DL duration, one residual OFDM symbolcan be further allocated to the UL duration, and the remaining oneresidual OFDM symbol can be allocated to the TTG duration. Thisalternative method is the same as the case of ¼ Tu, which was explainedwith a DL to UL ratio of 4:4 in FIG. 9.

In a second TDD frame structure of this embodiment, a CP length is 1/16Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 4175.73 Its, and includes43 OFDM symbols with a CP length of 1/16 Tu. A TTG duration is a timeperiod between the time point of 4175.73 i.ts and a time point of4260.23 μs, and thus includes a time period of 84.5 i.ts correspondingto a portion of the idle time and the TTG duration of Table. 2. A ULduration is a time period between the time point of 4260.23 i_ts and atime point of 4940 μs, and includes 7 OFDM symbols with a CP length of1/16 Tu. An RTG duration is a time period between the time point of 4940Rs and an end point of the frame, and thus includes a time period of 60i.ts corresponding to the RTG duration of Table 2. The time points maybe varied according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of a plurality of OFDM symbols, three residualOFDM symbols remain. Among the three residual OFDM symbols, one OFDMsymbol is further allocated to the DL duration, one OFDM symbol isfurther allocated to the UL duration, and the remaining one OFDM symbolis allocated between the 'FIG and RTG durations. In other words, thelast DL subframe is constructed of 7 OFDM symbols in FDD, and the lastsymbol in this subframe is punctured and is converted to a subframe of 6OFDM symbols in TDD due to the TTG duration. In the second TDD framestructure of FIG. 12, a first subframe of the DL duration is constructedof 7 OFDM symbols. However, any one subframe belonging to the DLduration can be constructed of 7 OFDM symbols instead of the firstsubframe. In addition, the DL duration can be constructed of a pluralityof subframes consisting of 6 OFDM symbols and the remaining oneindependent OFDM symbol. Such a subframe structure is for exemplarypurposes only. That is, the subframes belonging to the DL duration canbe constructed of any number of OFDM symbols, and the subframesbelonging to the UL duration can be constructed of any number of OFDMsymbols, wherein the subframes can have different sizes.

In a third TDD frame structure of this embodiment, a CP length is 1/32Tu. A total frame length is 5 ms. A DL duration is a time period betweena start point of a frame and a time point of 4241.7 las and includes 45OFDM symbols with a CP length of 1/32 Tu. A TTG duration is a timeperiod between the time point of 4241.7 Rs and a time point of 4280.18i.ts, and thus includes a time period of 38.48 Its corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 4280.18 gs and a time pointof 4940 pis, and includes 7 OFDM symbols with a CP length of 1/32 Tu. AnRTG duration is a time period between the time point of 4940 ps and anend point of the frame, and thus includes a time period of 60corresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations. Accordingly, if onesubframe is constructed of 6 OFDM symbols, 5 residual OFDM symbolsremain. Among the 5 residual OFDM symbols, 3 OFDM symbols are furtherallocated to the DL duration, one OFDM symbol is further allocated tothe UL duration, and the remaining one OFDM symbol is allocated betweenthe TTG and RTG durations. In the third TDD frame structure of FIG. 12,1^(st), 6^(th), and 7^(th) subframes of the DL duration are constructedof 7 OFDM symbols. However, any three subframes belonging to the DLduration can be constructed of 7 OFDM symbols instead of these threesubframes. In addition, the DL duration can be constructed of aplurality of subframes consisting of 6 OFDM symbols and the remainingthree independent OFDM symbols, and the UL duration can be constructedof a plurality of subframes consisting of 6 OFDM symbols and theremaining one independent OFDM symbol. Such a subframe structure is forexemplary purposes only. That is, the subframes belonging to the DLduration can be constructed of any number of OFDM symbols, and thesubframes belonging to the UL duration can be constructed of any numberof OFDM symbols, wherein the subframes can have different sizes.

If the TTG duration requires a longer duration than 38.48 ps, one ofOFDM symbols additionally allocated to the DL duration or the ULduration can be further allocated for the TTG duration. For example, oneof OFDM symbols additionally allocated to the UL duration can be furtherallocated for the TTG duration, and thus the TTG duration may be 132.74ps.

When the TDD frame is configured as shown in FIG. 12, mutualinterference does not occur even if the frame structures havingdifferent CP lengths exist in adjacent cells. That is, mutualinterference does not occur since a DL duration of a frame having a CPlength of ⅛ Tu does not overlap with a UL duration of a frame having aCP length of ¼ Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a framehaving a CP length of ⅛ Tu does not overlap with a DL duration of aframe having a CP length of ¼ Tu, 1/16 Tu, or 1/32 Tu.

Table 3 below summarizes some of the features shown in FIGS. 9-12 andshows a frame structure having a different CP length according to theabove-described embodiments of the invention and coexisting with aconventional reference frame structure.

TABLE 3 Parameters Values or Features MAR, Ratio with 4:4 5:3 6:2 7:14:4 5:3 6:2 7:1 4:4 5:3 6:2 7:1 a CP of ⅛ Tu CP lengths (us) ¼ Tu 1/16Tu 1/32 Tu Total No. of 43  51  53  Symbols per 5 ms Frame (Nsym) No. ofResidue 1 3 5 Symbols (=Nsym (In case of Nsym mod 5, mod 6) 3 ResidueSymbols) Positions of One in DL One in DL, One in UL, and Two in DL, Twoin UL, and Residue Symbols (In case of Nsym mod 5, One in TTG One in TTGOne in DL, One in UL (+)In case of 7:1, Three in DL, and One in TTG) Onein UL, and One in TTG (+) In case of 4:4, Two in DL, One in UL, and Twoin TTG No. of Punctured 1 0 0 Symbols in (In case of Nsym mod 5, Regular0 Punctured Symbol) Subframes Size of DL (ps) 2399.25 2856.25 3541.84227.25 2427.8 3010.41 3593.07 4175.73 2450.76 3016.32 3581.88 4241.7(Nsym mod 5) Size of UL (.ts) 2399.25 1942.25 5 571.25 2428.4 1845.091262.43 679.77 2356.5 1885.2 1319.64 659.82 (Nsym mod 5) No. of Regular5 6 4 Subframes (In case of Nsym mod 5, 6 Regular Subframes) Size ofIrregular 5 and 7 OFDM Symbols 7 OFDM Symbols 7 OFDM Symbols Subframes(*) (In case of Nsym mod 5, 6 OFDM Symbols) No. of Irregular 2 2 4Subframes (*)

In the TDD frame structure having a DL/UL ratio of 4:4 and having a CPlength of ¼ Tu shown in Table 3, it is assumed that one subframeconsists of 5 OFDM symbols, and one OFDM symbol is further allocated tothe TTG duration in the TDD frame structure having a CP length of 1/32Tu. In the TDD frame structure having a DL/UL ratio of 7:1 and having aCP length of 1/32 Tu, a residual OFDM symbol is further allocated to theUL duration since only one subframe is allocated for the DL duration. InTable 3, the last two rows indicated by a mark (*) vary according to thenumber of OFDM symbols constituting one subframe. When the configurationof Table 3 above is applied in systems, one symbol can be optionallyfurther punctured in a UL or DL duration.

<Type of Subframe Depending on the Number of OFDM Symbols Included inSubframe>

FIG. 13 to FIG. 16 each show 1) TDD frame structures from FIGS. 9 to 12,respectively, which has a different CP length and coexists with theaforementioned TDD frame structure having a CP length of ⅛ Tu in anadjacent cell, and 2) FDD frame structures having a common feature withthe TDD frame structures. A TDD frame and an FDD frame, each of whichhas a CP length of ¼ Tu, 1/16 Tu, or 1/32 Tu, are configured using threetypes of subframes.

Hereinafter, a type of the subframe consisting of 6 OFDM symbols isreferred to as a subframe type-1 (SFT-1), a type of the subframeconsisting of 5 OFDM symbols is referred to as an SFT-2, and a type ofthe subframe consisting of 7 OFDM symbols is referred to as an SFT-3. AnSFT-3 type subframe has a format in which one OFDM symbol is added to anSFT-1 type subframe. The added OFDM symbol may precede or follow theSFT-1 type subframe, or may be located in the middle of the SFT-1 typesubframe. The added OFDM symbol may be used for control information(e.g., preambles, sounding, etc.) or for data.

FIG. 13 shows TDD frame structures having a CP length of ¼ Tu and FDDframe structures having a common feature with the TDD frame structuresaccording to an embodiment of the present invention. In FIG. 13,subframes other than the SFT-2 type and SFT-3 type subframes are SFT-1type subframes.

Referring to FIG. 13, in a first TDD frame structure of this embodiment,a DL/UL ratio is 4:3 and a CP length is ¼ Tu. A total frame length is 5ms. A DL duration is a time period between a start point of a frame anda time point of 2856.25 μs, and includes 25 OFDM symbols with a CPlength of ¼ Tu. A TTG duration is a time period between the time pointof 2856.25 _(Its) and a time point of 2997.75 p.s, and thus includes atime period of 141.5 μs corresponding to a portion of the idle time andthe TTG duration of Table. 2. A UL duration is a time period between thetime point of 2997.75 Rs and a time point of 4940 μs, and includes 17OFDM symbols with a CP length of ¼ Tu. An RTG duration is a time periodbetween the time point of 4940 μs and an end point of the frame, andthus includes a time period of 60 μs corresponding to the RTG durationof Table 2. The time points may be varied according to the TTG and RTGdurations.

Accordingly, the DL duration consists of three SFT-1 subframes and oneSFT-3 subframe, and the UL duration consists of two SFT-1 subframes andone SFT-2 subframe. In this case, there is no restriction on a subframetype arrangement within the UL duration and the DL duration.

In a second TDD frame structure of this embodiment, a DL/UL ratio is 5:2and a CP length is ¼ Tu. A total frame length is 5 ms. A DL duration isa time period between a start point of a frame and a time point of3541.8 las, and includes 31 OFDM symbols with a CP length of ¼ Tu. A TTGduration is a time period between the time point of 3541.8 ps and a timepoint of 3683.25 tts, and thus includes a time period of 141.45 μscorresponding to a portion of the idle time and the TTG duration ofTable. 2. A UL duration is a time period between the time point of3683.25 Its and a time point of 4940 μs, and includes 11 OFDM symbolswith a CP length of ¼ Tu. An RTG duration is a time period between thetime point of 4940 μs and an end point of the frame, and thus includes atime period of 60 μs corresponding to the RTG duration of Table 2. Thetime points may be varied according to the TTG and RTG durations.

Accordingly, the DL duration consists of four SFT-1 subframes and oneSFT-3 subframe, and the UL duration consists of one SFT-1 subframe andone SFT-2 subframe. In this case, there is no restriction on a subframetype arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:1and a CP length is ¼ Tu. A total frame length is 5 ms. A DL duration isa time period between a start point of a frame and a time point of4227.25 μs, and includes 37 OFDM symbols with a CP length of ¼ Tu. A TTGduration is a time period between the time point of 4227.25;Is and atime point of 4368.75 μs, and thus includes a time period of 141.5 lascorresponding to a portion of the idle time and the TTG duration ofTable. 2. A UL duration is a time period between the time point of4368.75 μs and a time point of 4940 μs, and includes 5 OFDM symbols witha CP length of ¼ Tu. An RTG duration is a time period between the timepoint of 4940 Its and an end point of the frame, and thus includes atime period of 60 μs corresponding to the RTG duration of Table 2. Thetime points may be varied according to the TTG and RTG durations.

Accordingly, the DL duration consists of five SFT-1 subframes and oneSFT-3 subframe, and the UL duration consists of one SFT-2 subframe. Inthis case, there is no restriction on a subframe type arrangement withinthe UL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch durationcan conform to a frame structure having a CP length of ⅛ Tu. Thus, evenif a system having a CP length of ⅛ Tu exists in an adjacent cell,interference between uplink and downlink transmissions can be minimized.

Irrespective of a DL/UL ratio, the DL duration includes one SFT-3 typesubframe. In FIG. 13, a first subframe #1 of the DL duration isconstructed of one SFT-3 type subframe, but this is for exemplarypurposes only. That is, if the DL/UL ratio is 4:3, the SFT-3 typesubframe can be located at one position selected from positions #1, #2,#3, and #4. If the DL/UL ratio is 5:2, the SFT-3 type subframe can belocated at one position selected from positions #1, #2, #3, #4, and #5.If the DL/UL ratio is 6:1, the SFT-3 type subframe can be located at oneposition selected from positions #1, #2, #3, #4, #5, and #6.

In addition, irrespective of a DL/UL ratio, the UL duration includes oneSFT-2 type subframe. In FIG. 13, a first subframe #1 of the UL durationis constructed of the SFT-2 type subframe, but this is for exemplarypurposes only. That is, if the DL/UL ratio is 4:3, the SFT-2 typesubframe can be located at one position selected from positions #5, #6,and #7, if the DL/UL ratio is 5:2, the SFT-2 type subframe can belocated at one position selected from positions #6 and #7, and if theDL/UL ratio is 6:1, the SFT-2 type subframe can be located at a position#7.

Next, in the FDD frame structure, the FDD frame includes one pivotsubframe. The pivot subframe is a subframe located at a positioncorresponding to a TTG duration of the TDD frame so as to maintain acommon feature with the TDD frame. When the CP length is ¼ Tu, the pivotsubframe is an SFT-1 type subframe. If the DL/UL ratio is 4:3, the TTGduration in the TDD frame is located between positions #4 and #5, andthus the pivot subframe in the FDD frame can be located at a position#5. If the DL/UL ratio is 5:2, the TTG duration in the TDD frame islocated between positions #5 and #6, and thus the pivot subframe in theFDD frame can be located at a position #6. If the DL/UL ratio is 6:1,the TTG duration in the TDD frame is located between positions #6 and#7, and thus the pivot subframe in the FDD frame can be located at aposition #7. To maintain the common feature with the TDD frame, oneSFT-3 type subframe is located ahead of the pivot subframe. That is, ifthe DL/UL ratio is 4:3, the SFT-3 type subframe can be located at oneposition selected from positions #1, #2, #3, and #4, if the DL/UL ratiois 5:2, the SFT-3 type subframe can be located at one position selectedfrom positions #1, #2, #3, #4, and #5, and if the DL/UL ratio is 6:1,the SFT-3 type subframe can be located at one position selected frompositions #1, #2, #3, #4, #5, and #6.

In FIG. 13, the pivot subframe is only located in #5, #6, and #7. Butthis is for exemplary purposes only. The other FDD frame with differentlocations of the pivot subframe may be considered in the same way.

In FIG. 13, a base subframe is constructed of an SFT-1 type subframe inthe TDD frame structure having a CP length of ¼ Tu. The base subframemay be constructed of an SFT-2 type subframe.

FIG. 14 shows a TDD frame having a CP length of ¼ Tu and including abase subframe constructed of an SFT-2 type subframe and an FDD framehaving a common feature with the TDD frame. In FIG. 14, subframes otherthan the SFT-1 type subframes are SFT-2 type subframes.

Referring to FIG. 14, in a first TDD frame structure of this embodiment,a DL/UL ratio is 4:4, a CP length is ¼ Tu, and a base subframe isconstructed of an SFT-2 type subframe. This structure is the same as theTDD frame structure having a CP length of ¼ Tu as shown in FIG. 9.Accordingly, a DL duration consists of one SFT-1 subframe and threeSFT-3 subframes, and a UL duration consists of one SFT-1 subframe andthree SFT-2 subframes. In this case, there is no restriction on asubframe type arrangement within the UL duration and the DL duration.

In a second TDD frame of this embodiment, a DL/UL ratio is 5:3, a CPlength is ¼ Tu, and a base subframe is constructed of an SFT-2 typesubframe. A total frame length is 5 ms. A DL duration is a time periodbetween a start point of a frame and a time point of 2970.5 gs andincludes 26 OFDM symbols with a CP length of ¼ Tu. A TTG duration is atime period between the time point of 2970.5 gs and a time point of 3112gs, and thus includes a time period of 141.5 ps corresponding to aportion of the idle time and the TTG duration of Table. 2. A UL durationis a time period between the time point of 3112 gs and a time point of4940 gs, and includes 16 OFDM symbols with a CP length of ¼ Tu. An RTGduration is a time period between the time point of 4940 gs and an endpoint of the frame, and thus includes a time period of 60 gscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations.

Accordingly, a DL duration consists of one SFT-1 subframe and four SFT-2subframes, and a UL duration consists of one SFT-1 subframe and twoSFT-2 subframes. In this case, there is no restriction on a subframetype arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:2,a CP length is ¼ Tu, and a base subframe is constructed of an SFT-2 typesubframe. This structure is the same as the TDD frame structure having aCP length of ¼ Tu as shown in FIG. 11. Accordingly, a DL durationconsists of one SFT-1 subframe and five SFT-2 subframes, and a ULduration consists of one SFT-1 subframe and one SFT-2 subframe. In thiscase, there is no restriction on a subframe type arrangement within theUL duration and the DL duration.

In a fourth TDD frame structure of this embodiment, a DL/UL ratio is7:1, a CP length is ¼ Tu, and a base subframe is constructed of an SFT-2type subframe. A total frame length is 5 ms. A DL duration is a timeperiod between a start point of a frame and a time point of 4113 p.s,and includes 36 OFDM symbols with a CP length of ¼ Tu. A TTG duration isa time period between the time point of 4113 μs and a time point of4254.5 μs, and thus includes a time period of 141.5 gs corresponding toa portion of the idle time and the TTG duration of Table. 2. A ULduration is a time period between the time point of 4254.5 ps and a timepoint of 4940 [is, and includes 6 OFDM symbols with a CP length of ¼ Tu.An RTG duration is a time period between the time point of 4940 pis andan end point of the frame, and thus includes a time period of 60 1..tscorresponding to the RTG duration of Table 2. The time points may bevaried according to the TTG and RTG durations.

Accordingly, a DL duration consists of one SFT-1 subframe and six SFT-2subframes, and a UL duration consists of one SFT-1 subframe. In thiscase, there is no restriction on a subframe type arrangement within theUL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch durationcan conform to a frame structure having a CP length of ⅛ Tu. Thus, evenif a system having a CP length of ⅛ Tu exists in an adjacent cell,interference between uplink and downlink transmissions can be minimized.

If the base subframe is constructed of the SFT-2 type subframe, the DLduration includes one SFT-1 type subframe irrespective of a DL/UL ratio.If the DL/UL ratio is 4:4, the SFT-1 type subframe can be located at oneposition selected from positions #1, #2, #3, and #4. If the DL/UL ratiois 5:3, the SFT-1 type subframe can be located at one position selectedfrom positions #1, #2, #3, #4, and #5. If the DL/UL ratio is 6:2, theSFT-3 type subframe can be located at one position selected frompositions #1, #2, #3, #4, #5, and #6. If the DL/UL ratio is 7:1, theSFT-1 type subframe can be located at one position selected frompositions #1, #2, #3, #4, #5, #6, and #7.

If the base subframe is constructed of the SFT-2 type subframe, the ULduration includes one SFT-1 type subframe irrespective of a DL/UL ratio.If the DL/UL ratio is 4:4, the SFT-1 type subframe can be located at oneposition selected from positions #5, #6, #7, and #8. If the DL/UL ratiois 5:3, the SFT-1 type subframe can be located at one position selectedfrom positions #6, #7, and #8. If the DL/UL ratio is 6:2, the SFT-3 typesubframe can be located at one position selected from positions #7 and#8. If the DL/UL ratio is 7:1, the SFT-1 type subframe can be located ata position #8.

Next, in the FDD frame structure in which a CP length is ¼ Tu and a basesubframe is constructed of an SFT-2 subframe, the pivot subframe can belocated at a position corresponding to a TTG duration of the TDD frame.Herein, the pivot subframe is an SFT-1 type subframe. If the DL/UL ratiois 4:4, the TTG duration in the TDD frame is located between positions#4 and #5, and thus the pivot subframe in the FDD frame can be locatedat a position #4 or #5. If the DL/UL ratio is 5:3, the TTG duration inthe TDD frame is located between positions #5 and #6, and thus the pivotsubframe in the FDD frame can be located at a position #5 or #6. If theDL/UL ratio is 6:2, the TTG duration in the TDD frame is located betweenpositions #6 and #7, and thus the pivot subframe in the FDD frame can belocated at a position #6 or #7. If the DL/UL ratio is 7:1, the TTGduration in the TDD frame is located between positions #7 and #8, andthus the pivot subframe in the FDD frame can be located at a position #7or #8. However, since the UL duration includes one SFT-1 type subframe,if the DL/UL ratio is 7:1, the pivot subframe is preferably located atthe position #7.

To maintain the common feature with the TDD frame, one SFT-1 typesubframe is located ahead of the pivot subframe, and one SFT-1 typesubframe is located behind of the pivot subframe. That is, if the DL/ULratio is 4:4, when the pivot subframe is located at a position #4, theSFT-1 type subframes other than the pivot subframe can be located at oneposition selected from positions #1, #2, and #3 and at one positionselected from positions #5, #6, #7, and #8, or when the pivot subframeis located at the position #5, the SFT-1 type subframes can be locatedat one position selected from positions #1, #2, #3, and #4 and at oneposition selected from positions #6, #7, and #8. If the DL/UL ratio is5:3, when the pivot subframe is located at a position #5, the SFT-1 typesubframes other than the pivot subframe can be located at one positionselected from positions #1, #2, #3, and #4 and at one position selectedfrom positions #6, #7, and #8, or when the pivot subframe is located atthe position #6, the SFT-1 type subframes can be located at one positionselected from positions #1, #2, #3, #4, and #5 and at one positionselected from positions #7 and #8. If the DL/UL ratio is 6:2, when thepivot subframe is located at a position #6, the SFT-1 type subframesother than the pivot subframe can be located at one position selectedfrom positions #1, #2, #3, #4, and #5 and at one position selected frompositions #7 and #8, or when the pivot subframe is located at theposition #7, the SFT-1 type subframes can be located at one positionselected from positions #1, #2, #3, #4, #5, and #6 and at a position #8.If the DL/UL ratio is 7:1, when the pivot subframe is located at aposition #7, the SFT-1 type subframes other than the pivot subframe canbe located at one position selected from positions #1, #2, #3, #4, #5,and #6 and at a position #8, or when the pivot subframe is located atthe position #8, the SFT-1 type subframes can be located at twopositions selected from positions #1, #2, #3, #4, #5, #6, and #7.

In FIG. 14, the pivot subframe is only located in #5, #6, #7, and #8.But this is for exemplary purposes only. The other FDD frame withdifferent locations of the pivot subframe may be considered in the sameway.

FIG. 15 shows TDD frame structures having a CP length of 1/16 Tu and FDDframe structures having a common feature with the TDD frame structuresaccording to an embodiment of the present invention. In FIG. 15,subframes other than the SFT-3 type subframes are SFT-1 type subframes.

Referring to FIG. 15, in a first TDD frame structure of this embodiment,a DL/UL ratio is 4:4 and a CP length is 1/16 Tu. This structure is thesame as the TDD frame structure having a CP length of 1/16 Tu as shownin FIG. 9. Accordingly, a DL duration consists of one SFT-3 subframe andthree SFT-1 subframes, and a UL duration consists of one SFT-3 subframeand three SFT-1 subframes. In this case, there is no restriction on asubframe type arrangement within the UL duration and the DL duration.

In a second TDD frame structure of this embodiment, a DL/UL ratio is 5:3and a CP length is 1/16 Tu. This structure is the same as the TDD framestructure having a CP length of 1/16 Tu as shown in FIG. 10.Accordingly, a DL duration consists of one SFT-3 subframe and four SFT-1subframes, and a UL duration consists of one SFT-3 subframe and twoSFT-1 subframes. In this case, there is no restriction on a subframetype arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:2and a CP length is 1/16 Tu. This structure is the same as the TDD framestructure having a CP length of 1/16 Tu as shown in FIG. 11.Accordingly, a DL duration consists of one SFT-3 subframe and five SFT-1subframes, and a UL duration consists of one SFT-3 subframe and oneSFT-1 subframe. In this case, there is no restriction on a subframe typearrangement within the UL duration and the DL duration.

In a fourth TDD frame structure of this embodiment, a DL/UL ratio is 7:1and a CP length is 1/16 Tu. This structure is the same as the TDD framestructure having a CP length of 1/16 Tu as shown in FIG. 12.

Accordingly, a DL duration consists of one SFT-3 subframe and six SFT-1subframes, and a UL duration consists of one SFT-3 subframe. In thiscase, there is no restriction on a subframe type arrangement within theUL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch durationcan conform to a frame structure having a CP length of ⅛ Tu. Thus, evenif a system having a CP length of ⅛ Tu exists in an adjacent cell,interference between uplink and downlink transmissions can be minimized.

Irrespective of a DL/UL ratio, the DL duration includes one SFT-3 typesubframe. In FIG. 15, a first subframe #1 of the DL duration isconstructed of the SFT-3 type subframe, but this is for exemplarypurposes only. That is, if the DL/UL ratio is 4:4, the SFT-3 typesubframe can be located at one position selected from positions #1, #2,#3, and #4. If the DL/UL ratio is 5:3, the SFT-3 type subframe can belocated at one position selected from positions #1, #2, #3, #4, and #5.If the DL/UL ratio is 6:2, the SFT-3 type subframe can be located at oneposition selected from positions #1, #2, #3, #4, #5, and #6. If theDL/UL ratio is 7:1, the SFT-3 type subframe can be located at oneposition selected from positions #1, #2, #3, #4, #5, #6, and #7.

In addition, irrespective of a DL/UL ratio, the DL duration includes oneSFT-3 type subframe. In FIG. 15, a last subframe #8 of the UL durationis constructed of the SFT-3 type subframe, but this is for exemplarypurposes only.

That is, if the DL/UL ratio is 4:4, the SFT-3 type subframe can belocated at one position selected from positions #5, #6, #7, and #8. Ifthe DL/UL ratio is 5:3, the SFT-3 type subframe can be located at oneposition selected from positions #6, #7, and #8. If the DL/UL ratio is6:2, the SFT-3 type subframe can be located at one position selectedfrom positions #7 and #8. If the DL/UL ratio is 7:1, the SFT-3 typesubframe can be located at a position #8.

Next, in the FDD frame structure, the FDD frame includes one pivotsubframe. As shown in FIG. 15, the pivot subframe may be an SFT-3 typesubframe. The pivot subframe may be located at a position correspondingto a TTG duration of the TDD frame. That is, if the DL/UL ratio is 4:4,the TTG duration in the TDD frame is located between positions #4 and#5, and thus the pivot subframe in the FDD frame can be located at aposition #4 or #5. If the DL/UL ratio is 5:3, the TTG duration in theTDD frame is located between positions #5 and #6, and thus the pivotsubframe in the FDD frame can be located at a position #5 (preferably)or position #6. If the DL/UL ratio is 6:2, the TTG duration in the TDDframe is located between positions #6 and #7, and thus the pivotsubframe in the FDD frame can be located at a position #6 or #7. If theDL/UL ratio is 7:1, the TTG duration in the TDD frame is located betweenpositions #7 and #8, and thus the pivot subframe in the FDD frame can belocated at a position #7 or #8. However, since the UL duration includesone SFT-3 type subframe, if the DL/UL ratio is 7:1, the pivot subframeis preferably located at the position #7.

To maintain the common feature with the TDD frame, one SFT-3 typesubframe is located ahead of the pivot subframe, and one SFT-3 typesubframe is located behind of the pivot subframe. That is, if the DL/ULratio is 4:4, when the pivot subframe is located at a position #4, theSFT-3 type subframes other than the pivot subframe can be located at oneposition selected from positions #1, #2, and #3 and at one positionselected from positions #5, #6, #7, and #8, or when the pivot subframeis located at the position #5, the SFT-3 type subframes can be locatedat one position selected from positions #1, #2, #3, and #4 and at oneposition selected from positions #6, #7, and #8. If the DL/UL ratio is5:3, when the pivot subframe is located at a position #5, the SFT-3 typesubframes other than the pivot subframe can be located at one positionselected from positions #1, #2, #3, and #4 (preferably position #1) andat one position selected from positions #6, #7, and #8 (preferablyposition #8), or when the pivot subframe is located at the position #6,the SFT-3 type subframes can be located at one position selected frompositions #1, #2, #3, #4, and #5 and at one position selected frompositions #7 and #8. If the DL/UL ratio is 6:2, when the pivot subframeis located at a position #6, the SFT-3 type subframes other than thepivot subframe can be located at one position selected from positions#1, #2, #3, #4, and #5 and at one position selected from positions #7and #8, or when the pivot subframe is

located at the position #7, the SFT-3 type subframes can be located atone position selected from positions #1, #2, #3, #4, #5, and #6 and at aposition #8. If the DL/UL ratio is 7:1, when the pivot subframe islocated at a position #7, the SFT-3 type subframes other than the pivotsubframe can be located at one position selected from positions #1, #2,#3, #4, #5, and #6 and at a position #8.

In FIG. 15, the pivot subframe is only located in #4, #5, #6, and #7.But this is for exemplary purposes only. The other FDD frame withdifferent locations of the pivot subframe may be considered in the sameway.

FIG. 16 shows a TDD frame structure having a CP length of 1/32 Tu and anFDD frame structure having a common feature with the TDD frame structureaccording to an embodiment of the present invention. In FIG. 16,subframes other than the SFT-3 type subframes are SFT-1 type subframes.

Referring to FIG. 16, in a first TDD frame structure of this embodiment,a DL/UL ratio is 4:4 and a CP length is 1/32 Tu. A total frame length is5 ms. A DL duration is a time period between a start point of a frameand a time point of 2450.76 μs, and includes 26 OFDM symbols with a CPlength of 1/32 Tu. A TTG duration is a time period between the timepoint of 2450.76 μs and a time point of 2489.24 μs, and thus includes atime period of 38.48 tts corresponding to a portion of the idle time andthe TTG duration of Table. 2. A UL duration is a time period between thetime point of 2489.24 [Ls and a time point of 4940 ps, and includes 26OFDM symbols with a CP length of 1/32 Tu. An RTG duration is a timeperiod between the time point of 4940 ps and an end point of the frame,and thus includes a time period of 60 ps corresponding to the RTGduration of Table 2.

Accordingly, the DL duration consists of two SFT-3 subframes and twoSFT-1 subframes, and the UL duration consists of two SFT-3 subframes andtwo SFT-1 subframes. In this case, there is no restriction on a subframetype arrangement within the UL duration and the DL duration.

In a second TDD frame structure of this embodiment, a DL/UL ratio is 5:3and a CP length is 1/32 Tu. This structure is the same as the framestructure having a CP length of 1/32 Tu as shown in FIG. 10.Accordingly, a DL duration consists of two SFT-3 subframes and threeSFT-1 subframes, and a UL duration consists of two SFT-3 subframes andone SFT-1 subframe. In this case, there is no restriction on a subframetype arrangement within the UL duration and the DL duration.

In a third TDD frame structure of this embodiment, a DL/UL ratio is 6:2and a CP length is 1/32 Tu. This structure is the same as the framestructure having a CP length of 1/32 Tu as shown in FIG. 11.Accordingly, a DL duration consists of two SFT-3 subframes and fourSFT-1 subframes, and a UL duration consists of two SFT-3 subframes. Inthis case, there is no restriction on a subframe type arrangement withinthe UL duration and the DL duration.

In a fourth TDD frame structure of this embodiment, a DL/UL ratio is 7:1and a CP length is 1/32 Tu. This structure is the same as the framestructure having a CP length of 1/32 Tu as shown in FIG. 12.Accordingly, a DL duration consists of three SFT-3 subframes and fourSFT-1 subframes, and a UL duration consists of one SFT-3 subframe. Inthis case, there is no restriction on a subframe type arrangement withinthe UL duration and the DL duration.

By configuring the TDD frame as described above, a DL/UL switch durationcan conform to a frame structure having a CP length of ⅛ Tu. Thus, evenif a system having a CP length of ⅛ Tu exists in an adjacent cell,interference between uplink and downlink transmissions can be minimized.

The DL duration includes a plurality of SFT-3 type subframes. If theDL/UL ratio is 4:4, the SFT-3 type subframes can be located at twopositions selected from positions #1, #2, #3, and #4. If the DL/UL ratiois 5:3, the SFT-3 type subframes can be located at two positionsselected from positions #1, #2, #3, #4, and #5. If the DL/UL ratio is6:2, the SFT-3 type subframes can be located at two positions selectedfrom positions #1, #2, #3, #4, #5, and #6. If the DL/UL ratio is 7:1,the SFT-3 type subframes can be located at three positions selected frompositions #1, #2, #3, #4, #5, #6, and #7.

In addition, the UL duration includes a plurality of SFT-3 typesubframes. If the DL/UL ratio is 4:4, the SFT-3 type subframes can belocated at two positions selected from positions #5, #6, #7, and #8. Ifthe DL/UL ratio is 5:3, the SFT-3 type subframes can be located at twopositions selected from positions #6, #7, and #8. If the DL/UL ratio is6:2, the SFT-3 type subframes can be located at positions #7 and #8. Ifthe DL/UL ratio is 7:1, the SFT-3 type subframe can be located at aposition #8.

If the TTG duration requires a longer duration than 38.48 j.ts, two OFDMsymbols can be allocated to the TTG duration. For example, one of OFDMsymbols of the UL duration can be further allocated for the TTGduration, and thus the TTG duration may be 132.74 Its. In this case, ifthe DL/UL ratio is 4:4, the SFT-3 type subframes can be located at twopositions selected from #1, #2, #3, and #4 and at one position selectedfrom positions #5, #6, #7, and #8. If the DL/UL ratio is 5:3, the SFT-3type subframes can be located at two positions selected from positions#1, #2, #3, #4, and #5 and at one position selected from positions #6,#7, and #8. If the DL/UL ratio is 6:2, the SFT-3 type subframes can belocated at two positions selected from #1, #2, #3, #4, #5, and #6 and atone position selected from positions #7 and #8. If the DL/UL ratio is7:1, the SFT-3 type subframes can be located at two positions selectedfrom positions #1, #2, #3, #4, #5, #6, and #7 and at a position #8.

Next, in the FDD frame structure, the FDD frame includes one pivotsubframe. As shown in FIG. 16, the pivot subframe may be an SFT-3 typesubframe. The pivot subframe may be located at a position correspondingto a TTG duration of the TDD frame. That is, if the DL/UL ratio is 4:4,the TTG duration in the TDD frame is located between positions #4 and#5, and thus the pivot subframe in the FDD frame can be located at aposition #4 or #5. If the DL/UL ratio is 5:3, the TTG duration in theTDD frame is

located between positions #5 and #6, and thus the pivot subframe in theFDD frame can be located at a position #5 or #6. If the DL/UL ratio is6:2, the TTG duration in the TDD frame is located between positions #6and #7, and thus the pivot subframe in the FDD frame can be located at aposition #6 or #7. However, since the UL duration includes two SFT-3type subframes, the pivot subframe is preferably located at the position#6. If the DL/UL ratio is 7:1, the TTG duration in the TDD frame islocated between positions #7 and #8, and thus the pivot subframe in theFDD frame can be located at a position #7 or #8. However, since the ULduration includes one SFT-3 type subframe, the pivot subframe ispreferably located at the position #7.

To maintain the common feature with the TDD frame, two SFT-3 typesubframes are located ahead of the pivot subframe, and two SFT-3 typesubframes are located behind of the pivot subframe. That is, if theDL/UL ratio is 4:4, when the pivot subframe is located at a position #4,the SFT-3 type subframes other than the pivot subframe can be located attwo positions selected from positions #1, #2, and #3 and at twopositions selected from positions #5, #6, #7, and #8, or when the pivotsubframe is located at the position #5, the SFT-3 type subframes can belocated at two positions selected from positions #1, #2, #3, and #4 andat two positions selected from positions #6, #7, and #8. If the DL/ULratio is 5:3, when the pivot subframe is located at a position #5, theSFT-3 type subframes other than the pivot subframe can be located at twopositions selected from positions #1, #2, #3, and #4 and at twopositions selected from positions #6, #7, and #8, or when the pivotsubframe is located at the position #6, the SFT-3 type subframes can belocated at two positions selected from positions #1, #2, #3, #4, and #5and at positions #7 and #8. If the DL/UL ratio is 6:2, when the pivotsubframe is located at a position #6, the SFT-3 type subframes otherthan the pivot subframe can be located at two positions selected frompositions #1, #2, #3, #4, and #5 and at positions #7 and #8, or when thepivot subframe is located at the position #7, the SFT-3 type subframescan be located at three positions selected from positions #1, #2, #3,#4, #5, and #6 and at a position #8. If the DL/UL ratio is 6:2, when thepivot subframe is located at a position #7, the SFT-3 type subframesother than the pivot subframe can be located at three positions selectedfrom positions #1, #2, #3, #4, #5, and #6 and at a position #8, or whenthe pivot subframe is located at the position #8, the SFT-3 typesubframes can be located at four positions selected from positions #1,#2, #3, #4, #5, #6, and #7.

In FIG. 16, the pivot subframe is only located in #4, #5, #6, and #7.But this is for exemplary purposes only. The other FDD frame withdifferent locations of the pivot subframe may be considered in the sameway.

When the TDD frame is configured as shown in FIG. 13 to FIG. 16, mutualinterference does not occur even if the frame structures havingdifferent CP lengths exist in adjacent cells. That is, mutualinterference does not occur since a DL duration of a frame having a CPlength of ⅛ Tu does not overlap with a UL duration of a frame having aCP length of ¼ Tu, 1/16 Tu, or 1/32 Tu, and a UL duration of a framehaving a CP length of ⅛ Tu does not overlap with a DL duration of aframe having a CP length of ¼ Tu, 1/16 Tu, or 1/32 Tu.

Since the FDD frame configured as shown in FIG. 13 to FIG. 16 has acommon feature with the corresponding TDD frame, an algorithm used in aTDD system or a related communication algorithm (i.e., resourceallocation) can be reused in an FDD system.

Table 4 below summarizes some of the features of FIGS. 13-16 and shows acharacteristic of a TDD frame structure according to an embodiment ofthe present invention.

TABLE 41 Parameters Values or Features DL/UL Ratio 5:3 6:2 7:1 4:4 5:36:2 7:1 5:3 6:2 7:1 with a CP of ⅛ Tu CP lengths (us) ¼ Tu 1/16 Tu 1/32Tu TDD No. of SFT-1 5 6 4 Subframes No. of SFT-2 and 2 2 4 SFT-3Positions of SFT- Any position that avoids Any position that avoids theAny position that avoids the 1 Subframes the positions of SFT-2positions of SFT-2 and SFT-3 positions of SFT-2 and and SFT-3 SubframesSubframes SFT-3 Subframes Positions of SFT- #5 #6 #7 N/A N/A N/A N/A N/AN/A N/A 2 Subframes Positions of SFT- One One One One One One One TwoTwo Two 3 Subframes among among among among among among among amongamong among #1, #2, #1, #1, #1, #2, #3 #1, #1, #1, #1, #2, #1, #2, #1,#2, #3 #2, #2, and #4 + #2, #2, #2, #3, #3, #4, #3, #4, and #4 #3, #3,One #3, #3, #3, #4 #5 and #5, #6 #4 #4, 5 among #4 #4 #4, #5, and #5 +#6 + and #7 + and and #5, #6, #7 and #5 #6 Two #7 and #8 #5 #6 and #8#5 + and and among #8 One #6 + #7 + #6, #7 among One #8 and #8 #6, #7among and #8

Table 5 below summarizes features of FIGS. 13-16 and shows acharacteristic of a TDD frame having a structure in which a CP length is¼ Tu and a base subframe is constructed of an SFT-2 type subframeaccording to an embodiment of the present invention.

TABLE 5 Parameters Value or Features DL/UL Ratio with 4:4 5:3 6:2 7:1 aCP of ⅛Tu CP lengths (ps) ¼Tu No. of SFT-1 2 Subframes No. of SFT-2 and6 SFT-3 Subframes Positions of SFT-1 One among #1, #2, One among #1, #2,One among #1, #2, One among #1, #2, Subframes #3 and #4 + One #3, #4 and#5 + One #3, #4, #5 and #6 + One #3, #4, #5, #6 and among #5, #6, #7among #6, #7 and #8 among #7 and #8 #7 + #8 and #8 Positions of SFT-2Any position that avoids the positions of SFT-1 and SFT-3 SubframesSubframes Positions of SFT-3 N/A Subframes

Table 6 below summarizes features of FIGS. 13-16 and shows acharacteristic of a TDD frame having a structure in which a CP length is1/32 Tu and two OFDM symbols are allocated to a TTG duration accordingto an embodiment of the present invention.

TABLE 6 Parameters Values or Features DL/UL Ratio with 4:4 5:3 6:2 7:1 aCP of ⅛Tu CP lengths (μs) 1/32Tu No. of SFT-1 5 Subframes No. of SFT-2and 3 SFT-3 Subframes Positions of Any position that avoids thepositions of SFT-2 and SFT-3 Subframes SFT-1 Subframes Positions of N/ASFT-2 Subframes Positions of SFT- Two among #1, #2, Two among #1, #2,Two among #1, #2, Two among #1, 3 Subframes #3 and #4 + One #3, #4 and#5 + One #3, #4, #5 and #6 + #2, #3, #4, #5, #6 among #5, #6, #7 among#6, #7 and #8 One among #7 and and #7 + #8 and #8 #8

Table 7 below summarizes additional features of FIGS. 13-16 and shows acharacteristic of an FDD frame structure according to an embodiment ofthe present invention.

TABLE 7 Parameters Values or Features DL/UL 5:3 6:2 7:1 4:4 5:3 6:2 7:15:3 6:2 7:1 Ratio with a CP of ⅛ Tu CP ¼ Tu 1/16 Tu 1/32 Tu lengths(p,FDD No. of 6 5 3 SFT-1 Subframes No. of 1 3 4 SFT-2 and SFT-3 Type ofSFT-1 SFT-3 SFT-3 Pivot Subframes Positions #5 #6 #7 #4 #5 #6 #7 #5 #6#7 of Pivot Subframe (Option 1) Positions #5 #6 #7 #6 of Pivot Subframe(Option 2) Positions Any position that avoids the Except the positionsof SFT-2 Except the positions of SFT-2 of SFT-1 positions of SFT-2 andSFT-3 and SFT-3 Subframes and SFT-3 Subframes Subframes SubframesPositions N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A of SFT-2 SubframesPositions One One One One One One One Two Two Three of SFT-3 among among#1, among among among among among among #1, among #1, #2, amongSubframes #1, #2, #2, #3, #4 #1, #2, #1, #2 #1, #2, #1, #2, #1, #2, #2,#3 and #3, #4 and #1, #2, for #3 and and #5 #3, #4, #5 and #3 + #3, and#3, #4 #3, #4, #4 + Two #5 + #7 #3, #4, #5 Option 1 #4 and #6 One #4 +and #5 + #5 and among #6, and #8 and #6 + among One One #6 + #8 #7 and#8 #8 #5, #6, among among #7 and #6, #7 #7 and #8 and #8 #8 Positions 1Option#4 Same as Same One One Same Two Same as Same as of SFT-3 Same asOption 1 as among among among as #1, Option 1 Option 1 Subframes Option1 One #1, #2, #1, #2, Option 1 #2, #3, #4 for among#1, #3, #4 and #3,#4, #7 and #5 + Option 2 #2, #3 and + #5 + One #5 and and #8 One among#6 + #8 among #7 and #6, #7 #8 and #8

Table 8 below summarizes additional features of FIGS. 13-16 and shows acharacteristic of an FDD frame having a structure in which a CP lengthis ¼ Tu and a base subframe is constructed of an SFT-2 type subframeaccording to an embodiment of the present invention.

TABLE 8 Parameters Values or Features DL/UL Ratio with 4:4 5:3 6:2 7:1 aCP of ⅛Tu CP lengths (p) ¼Tu No. of SFT-1 3 Subframes No. of SFT-2 and 5SFT-3 Subframes Type of Pivot SFT-1 Subframe Positions of Pivot #4 #5 #6#7 Subframes (Option 1) Positions of Pivot #5 #6 #7 Subframes (Option 2)Positions of SFT- Any position that avoids the positions of SFT-2 andSFT-3 Subframes 1 Subframes Positions of SFT-2 Two among #1, #2 Threeamong #1, #2, Four among #1, #2, Five among #1, #2, Subframes (Optionand #3 + Three #3 and #4 + Two #3, #4 and #5 + One #3, #4, #5 and #6 1)among #5, #6, #7 among #6, #7 and #8 among #7 and #8 and #8 Positions ofSFT-2 Three among #1, #2, Four among #1, #2, Five among #1, #2,Subframes (Option #3 and #4 + Two #3, #4 and #5 + One #3, #4, #5 and #62) among #6, #7 and #8 among #7 and #8 Positions of SFT-3 N/A N/A N/AN/A Subframes

Table 9 below summarizes additional features of FIGS. 13-15 and shows acharacteristic of an FDD frame having a structure in which a CP lengthis 1/32 Tu and two OFDM symbols are allocated to a TTG durationaccording to an embodiment of the present invention.

TABLE 9 Parameters Values or Features DL/UL Ratio with 4:4 5:3 6:2 7:1 aCP of ⅛Tu CP lengths (p) 1/32Tu No. of SFT-1 4 Subframes No. of SFT-2and 4 SFT-3 Subframes Type of Pivot SFT-3 Subframe Positions of Pivot #5#6 #7 #8 Subframes (Option 1) Positions of Pivot Subframes (Option 2)Positions of SFT- Any position that avoids the positions of SFT-2 andSFT-3 Subframes 1 Subframes Positions of SFT- N/A 2 Subframes Positionsof SFT-3 Two among #1, #2, Two among #1, #2, Two among #1, #2, Threeamong #1, #2, Subframes (Option #3 and #4 + One #3, #4 and #5 + One #3,#4, #5 and #6 + #3, #4, #5, #6 and #7 1) among #6, #7 and #8 among #7and #8 #8 Positions of SFT-3 Same as Option 1 Same as Option 1 Same asOption 1 Same as Option 1 Subframes (Option 2)

FIG. 17 is a block diagram showing an apparatus of wirelesscommunication that may be used with the previously describedembodiments. An apparatus 50 may be a part of UE. The apparatus 50includes a processor 51, a memory 52, a transceiver 53, a display 54,and a user interface unit 55. The processor 51 may be configured toconfigure at least one subframe in a frame. The frame may be constructedby the proposed schemes. The memory 52 is coupled with the processor 51and stores a variety of information to configure the at least onesubframe in the frame. The display 54 displays a variety of informationof the UE 50 and may use a well-known element such as a liquid crystaldisplay (LCD), an organic light emitting diode (OLED), etc. The userinterface unit 55 can be configured with a combination of well-knownuser interfaces such as a keypad, a touch screen, etc. The transceiver53 is coupled with the processor 51 and transmits and/or receives asubframe in the frame.

According to the present invention, when frame structures having variouscyclic prefix (CP) lengths and supporting an Institute of Electrical andElectronics Engineers (IEEE) 802.16m format coexist in adjacent cells,mutual interference can be mitigated in data transmission. The entirecontents of IEEE 802.16m is incorporated herein by reference.

In addition, by providing a frequency division duplexing (FDD) framestructure having a common feature with a time division duplexing (TDD)frame structure, an algorithm used in a TDD system or a relatedcommunication algorithm (i.e., resource allocation) can be reused in anFDD system.

The present invention can be implemented with hardware, software, orcombination thereof. In hardware implementation, the present inventioncan be implemented with one of an application specific integratedcircuit (ASIC), a digital signal processor (DSP), a programmable logicdevice (PLD), a field programmable gate array (FPGA), a processor, acontroller, a microprocessor, other electronic units, and combinationthereof, which are designed to perform the aforementioned functions. Insoftware implementation, the present invention can be implemented with amodule for performing the aforementioned functions. Software is storablein a memory unit and executed by the processor. Various means widelyknown to those skilled in the art can be used as the memory unit or theprocessor.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

1-12. (canceled)
 13. A method of transmitting data through atransmission frame, the method comprising: receiving a transmissionframe including a plurality of subframes from the transmitting unit, thesubframes being divided into at least two type of signals, wherein afirst type of signal includes a first number of OFDM symbol, and asecond type of signal includes a second number of OFDM symbol differentfrom the first number of OFDM symbol, wherein the second type of signalis located right after the first type of signal, and wherein thesubframes include a specific OFDM symbol, the specific OFDM symbolrepresenting a closing OFDM symbol.
 14. The method of claim 13, whereina sum of the first number and the second number varies depending on anFFT size of the OFDM symbol and a cyclic prefix length of the OFDMsymbol.